Codechange: Replace FOR_ALL_SIGNS with range-based for loops

src/economy.cpp

@@ -521,8 +521,7 @@ void ChangeOwnershipOfCompanyItems(Owner old_owner, Owner new_owner)
 		}
 	}
 
-	Sign *si;
-	FOR_ALL_SIGNS(si) {
+	for (Sign *si : Sign::Iterate()) {
 		if (si->owner == old_owner) si->owner = new_owner == INVALID_OWNER ? OWNER_NONE : new_owner;
 	}